1. Field of the Invention
The present invention relates to temperature measurement method and apparatus capable of realizing accurate temperature measurement of a measurement target object whose temperature is difficult to measure directly as it is a movable object to which a temperature sensor cannot be fixed directly but there is a need to monitor its temperature constantly or frequently, even when there is a transient temperature change.
2. Description of the Related Art
The most popular and simple method for measuring temperature of an object to which a temperature sensor cannot be set in contact directly such as a movable object is a method as shown in FIG. 10, in which an atmospheric temperature in vicinity of a measurement target object 101 is measured by a thermometer 103 by using a temperature sensor 102 arranged in vicinity of the measurement target object, 101 and this temperature is regarded as the temperature of the measurement target object 101. For the temperature sensor, a thermistor, a thermocouple, and a resistance temperature detector are often used. When a correspondence between the temperature sensor 102 and the temperature of the measurement target object 101 is calibrated in advance under a stable temperature condition such as that of a temperature controlled box, the temperature indicated by the thermometer 103 agrees with the actual temperature of the measurement target object 101 very well under a static environment.
Also, as a method for measuring temperature of a movable object including a transient temperature change, there is a method for measuring temperature indirectly by measuring another observation value which changes as the temperature changes. For example, when a radiation thermometer is used, the temperature can be measured according to infrared rays emitted from an object.
Also, when a measurement target object is an object through which lights can transmit, there is a method as shown in FIG. 11 in which temperature is measured according to a transmission wavelength which varies as the temperature of the object changes. FIG. 11 shows a method in which a white light from a white light source 202 is incident on a measurement target object 201 having a light transmitting characteristic, a transmission wavelength which varies as the temperature changes is observed by an optical spectrum analyzer 203, and the temperature is measured from a conversion table 204 between transmission wavelengths and temperatures, which is calibrated in advance.
As described above, in order to measure temperature of a measurement target object whose temperature is difficult to measure directly as it is a movable object to which a temperature sensor cannot be fixed directly but there is a need to monitor its temperature constantly or frequently, the methods as shown in FIG. 10 and FIG. 11 have been used conventionally. However, these conventional methods have drawbacks such as that the accurate temperature measurement cannot be realized when there is a transient temperature change, or that it is costly.
Namely, the method for measuring the temperature in vicinity of the measurement target object by using the temperature sensor and regarding this temperature as the temperature of the measurement target object has a drawback that, as shown in FIG. 10, there is a transient difference between the temperature characteristics 107 and 108 of the measurement target object 101 and the temperature sensor 102 due to a difference in the thermal capacity or the like, and there can be cases where this difference causes as a transient temperature error 109.
Also, the method for indirectly measuring the temperature of the measurement target object by measuring another observation value which varies as the temperature changes in a non-contact manner has a drawback that method and apparatus for measuring these observation values are more complicated, larger, and more costly, compared with the method using the temperature sensor.
For example, a temperature meter using a combination of a thermistor and a thermometer will only costs about several thousand yen, whereas one using an optical spectrum analyzer as shown in FIG. 11 will cost as much as several million yen. Consequently, from viewpoints of size and cost, it is not preferable to use a device such as the optical spectrum analyzer in the application that requires the constant or frequent temperature monitoring, although there can be cases where the optical spectrum analyzer is temporarily used in the application such as that for collecting temperature calibration data.
It is therefore an object of the present invention to provide a temperature measurement method capable of eliminating a transient temperature error that can be caused by the conventional temperature sensor, and a temperature meter using this method which is capable of measuring temperature accurately by using the conventional temperature sensor even under a transient circumstance in which temperature changes are frequent.
According to one aspect of the present invention there is provided a temperature measurement method for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: obtaining an observed temperature from the temperature sensor arranged in a vicinity of the measurement target object and a temperature observation time from a timer; and calculating the temperature of the measurement target object Tobj according to the observed temperature and the temperature observation time by a calculation processing based on a following equation (C):
Tobj(t1)=Ginxc2x7f(xcex94tobs)xc2x7xcex94tobs+Tobj(t0)xe2x80x83xe2x80x83(C)
where t1 is a current time at which the observed temperature is observed, t0 is a time at which temperature was measured last time, Gin is a time change rate of temperature applied to the measurement target object, f(xcex94tobs) is a polynomial regarding xcex94tobs, and xcex94tobs is a time interval by which temperature has been observed.
According to another aspect of the present invention there is provided a temperature meter for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: a temperature sensor configured to measure an observed temperature in a vicinity of the measurement target object; a timer configured to measure a temperature observation time; and a calculation processor configured to calculate the temperature of the measurement target object Tobj according to the observed temperature and the temperature observation time by a calculation processing based on a following equation (C):
Tobj(t1)=Ginxc2x7f(xcex94tobs)xc2x7xcex94tobs+Tobj(t0)xe2x80x83xe2x80x83(C)
where t1 is a current time at which the observed temperature is observed, t0 is a time at which temperature was measured last time, Gin is a time change rate of temperature applied to the measurement target object, f(xcex94tobs) is a polynomial regarding xcex94tobs, and xcex94tobs is a time interval by which temperature has been observed.
According to another aspect of the present invention there is provided a computer usable medium having computer readable program codes embodied therein for causing a computer to function as a temperature meter for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, the computer readable program codes include: a computer readable program code for causing said computer to calculate the temperature of the measurement target object Tobj according to an observed temperature obtained from a temperature sensor arranged in a vicinity of the measurement target object and a temperature observation time obtained from a timer, by a calculation processing based on a following equation (C):
Tobj(t1)=Ginxc2x7f(xcex94tobs)xc2x7xcex94tobs+Tobj(t0)xe2x80x83xe2x80x83(C)
where t1 is a current time at which the observed temperature is observed, t0 is a time at which temperature was measured last time, Gin is a time change rate of temperature applied to the measurement target object, f(xcex94tobs) is a polynomial regarding xcex94tobs, and xcex94tobs is a time interval by which temperature has been observed.
According to another aspect of the present invention there is provided a temperature measurement method for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: arranging another object which has transient temperature characteristics identical to those of the measurement target object, in a vicinity of the measurement target object; and measuring the temperature of the measurement target object according to an observed temperature obtained from the temperature sensor that is set in contact with the another object.
According to another aspect of the present invention there is provided a temperature meter for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: another object which has transient temperature characteristics identical to those of the measurement target object, and which is arranged in a vicinity of the measurement target object; and a temperature sensor that is set in contact with the another object, for measuring an observed temperature of the another object as the temperature of the measurement target object.
According to another aspect of the present invention there is provided a temperature measurement method for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: arranging a plurality of other objects which have mutually different transient temperature characteristics, in a vicinity of the measurement target object; and calculating the temperature of the measurement target object by weighted addition of observed temperatures obtained from a plurality of temperature sensors that are respectively set in contact with the plurality of other objects.
According to another aspect of the present invention there is provided a temperature meter for measuring temperature of a measurement target object to which a temperature sensor cannot be fixed directly, comprising: a plurality of other objects which have mutually different transient temperature characteristics, which are arranged in a vicinity of the measurement target object; a plurality of temperature sensors that are respectively set in contact with the plurality of other objects; and an adder configured to calculate the temperature of the measurement target object by weighted addition of observed temperatures obtained from the plurality of temperature sensors.
Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.